Pioneer 4 was a spin-stabilized spacecraft launched as part of the Pioneer program on a lunar flyby trajectory and into a heliocentric orbit making it the first U.S. probe to escape from the Earth's gravity. It carried a payload similar to Pioneer 3: a lunar radiation environment experiment using a Geiger-Müller tube detector and a lunar photography experiment. It passed within 60,000 km of the Moon's surface. However, Pioneer 4 did not come close enough to trigger its photoelectric sensor. The spacecraft was still in solar orbit as of 1969.
Read more about Pioneer 4: Spacecraft Design, Launching Vehicle, Mission
Famous quotes containing the word pioneer:
“Where the citizen uses a mere sliver or board, the pioneer uses the whole trunk of a tree.”
—Henry David Thoreau (1817–1862)